Institut für Energietechnik (IET)

Energy and Carbon Flows

Project team:

IET Institute for Energy Technology, HSR Rapperswil: Zoe Stadler, Boris Meier, Prof. Dr. Markus Friedl
IPESE Industrial Process and Energy Systems Engineering, EPFL Sion: Dr. Theodoros Damartzis, Xiang Li, Dr. Stefano Moret, Prof. Dr. François Maréchal

Around three-quarters of the energy demand in Switzerland is covered by imports. The upcoming energy transition causes uncertainties in regard of the future energy supply and to the desire for increasing the use of domestic energy sources. However, the potential of some resources like biomass is limited. For this reason, the Institute for Energy Technology IET at the University of Applied Sciences Rapperswil started the project "Carbon Flows in the Energy Transition". In collaboration with the EPFL in Sion, the IET examined the different energy and carbon sources in Switzerland and how to use them most efficiently to cover the demand. It shows for example that a carbon tax of 400 to 700 Francs per ton CO2 is necessary to enable a transition from fossil to renewable energy sources.

Carbon-based products without fossil carbon

In the context of the energy transition, there is much debate about energy flows and decarbonization. Little account is taken of the fact that carbon will continue to be indispensable for many applications after the energy transformation, such as plastics, chemical products and jet fuels. As source for these carbon based products, biomass as well as carbon dioxide can be used. While the potential of sustainable domestic biomass is limited, carbon dioxide is available in large amounts but rather expensive. For a successful energy turnaround, energy and product flows within Switzerland have to be investigated, with special regard to future demand.

Research project: "Carbon Flows in the Energy Transition"

In the project “Carbon Flows in the Energy Transition”, a methodology is developed to monitor and assess the energy and carbon flows in the energy system of Switzerland. As the flows of carbon, either in the form of released CO2 or stored in chemicals, are linked to the form and operation of the energy system, the design of the latter is crucial. Since the defossilization of the energy system is an important part to reach climate agreement goals, emphasis is given in renewables and biogenic carbon-containing resources, such as various forms of biomass and waste. The project takes a holistic approach and looks at all carbon flows associated to bio-based and fossil resources, flue gases, biofuels, biochemicals and plastics within Switzerland and across the borders (imports and exports).

The goal of this project is to look at the Swiss energy and carbon flows with a holistic approach and to research the following questions:

  • What are the carbon resources in Switzerland and what will be their role as products or energy carriers? How much biomass is there in Switzerland (sustainable potential)?
  • What are the available conversion technologies for biomass (cost, efficiencies, etc.)?
  • What are the most cost and environmentally efficient ways of using limited biomass resources to meet the decarbonization targets?
  • What are the technologies and the technoeconomic conditions of the integration of carbon sequestration and reuse in Switzerland?
  • What will be the role of carbon harvesting and reuse in the energy transition and what will be the impact in terms of fossil CO2 emissions?

Project procedure

To form a fossil-free future of Switzerland, policy makers have to take measures. To determine which measures are most effective, this project traces the carbon flows in Switzerland and evaluates different pathways depending on different operating scenarios. The answers given by the project in the context of designing the optimal energy system with respect to a variety of operating modes will hint towards the necessary actions to be taken for a successful implementation in a fossil-free future.

For the project, a dataset was elaborated that includes the potential of the most important carbon and energy sources in Switzerland as well as energy and carbon conversion technologies (around 120 in total). These technologies include power plants, technologies for heating, cogeneration, mobility and transport, as well as biomass technologies, power-to-X-technologies and others.

The resulting data is incorporated into the existing infrastructure of Swiss EnergyScope (SES), an optimization algorithm for the design of energy systems and applied for the case of Switzerland. With the adaption carried out in this project, this algorithm models and allocates energy and carbon flows, in order to design efficient energy systems and identify the optimal energy and carbon paths, from carbon source (e.g. biomass or carbon dioxide) to carbon-based products (e.g. plastics or fuels). The objective function of the optimization can include economic and/or ecological aspects and the produced results help to derive decisions regarding the energy policy that can ultimately lead to efficient political measures. Although this algorithm is targeted towards the modeling of the carbon flows with a case study of Switzerland, it is of a generic structure and can be adapted for other energy systems of different scales as well.

A selected number of indicative scenarios are presented that can be used to investigate the necessary future actions towards nuclear phasing-out, defossilization and CO2 taxation to name a few, with regard to the energy and carbon emissions profile of Switzerland.


A possible measure to establish carbon capture technologies is to charge a carbon dioxide tax on fossil fuels. Starting from the current import prises of fossil fuels, a price increase from 370 Fr./t CO2 for gasoline to 750 Fr./t CO2 for natural gas is necessary (560 Fr./t CO2 for jet fuel and oil, and 440 Fr./t CO2 for diesel). As soon as carbon capture technologies are further developed and installed in larger quantities, the costs will decline and with that the CO2 tax can be reduced as well. However, an effective transition requires the before mentioned taxes.

In addition an adaption of the current energy grid infrastructure is necessary including the installation of a lot of photovoltaic, wind and power-to-gas plants. This way, a controlled energy turnaraound and a decrease in the dependence on foreign energy suppliers can be achieved. At the same time, a reduction in the energy demand is needed. 

More information on the project:

In April 2018, the project “Carbon Flows in the Energy Transition” started as an extension of the project “Renewable Methane in Transport and Mobility (RMTM)”, and ended in May 2019. A team both from Hochschule für Technik Rapperswil (HSR) and from École Polytechnique Fédérale de Lausanne (EPFL) carried it out. The project is part of the National Research Programme NRP70 and financed by the Swiss National Science Foundation (SNF), the Swiss Federal Office of Energy (SFOE) and the Federal Office for the Environment (FOEN) as well as by own funds.


Zoe Stadler
+41 (0)55 222 43 03